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StringTools

  

ExpandCharacterClass

  

expand a character class to a string

 

Calling Sequence

Parameters

Description

Character Classes

Examples

Calling Sequence

ExpandCharacterClass( ccl )

Parameters

ccl

-

string; character class expression

Description

• 

The ExpandCharacterClass(ccl) command expands character class expressions as described in the following section. These expressions are used to describe sets of characters in wildcard and regular expression patterns, but may be used for other purposes as well.

• 

If the string ccl is a valid character class expression, then a string, with at most 255 characters, is returned that denotes literally the expressed character class.

Character Classes

  

In a character class expression, most characters denote themselves literally. For example, the character class expression abc denotes the character class consisting of the characters a, b and c, which is represented by the string abc. Likewise, the string bca, interpreted as a character class expression, denotes the character class abc, the only difference being the order in which the characters are presented. By convention, literal character classes are returned in code point order.

  

If a character in a character class expression is preceded by a backslash, it is escaped, meaning that any special significance attached to it for character class expressions is suppressed (for that specific instance in the expression only).

  

The first and last characters in a character class expression can be open and close brackets ([ and ]), respectively. In this case, the expression is equivalent to the one obtained by removing the first and last characters. If either of the characters [ and ] appear anywhere but at the beginning and end, respectively, of the character class expression, they are taken literally. For example, [ab]de] is equivalent to ab]de.

Character Ranges

  

A consecutive range of characters is denoted by an interposed hyphen (-). For example, a-d represents the character class abcd. The character to the left of the hyphen must precede the character to its right, in code point order. Thus, for example, z-a is invalid.

  

Character literals and ranges may be juxtaposed in a character class expression. For example, a-cwxyzd-h is a valid character class expression which expands to the literal character class abcdefghwxyz.

Negated Character Classes

  

If the first character in a character class expression is a caret (^) (or, if the character class expression is enclosed in brackets, and the caret follows the opening bracket), then the resulting character class is negated. This means that the character class expression expands to the set of characters not in the class described by the rest of the expression.

Named Character Classes

  

If the first and last characters of a character class expression are colons (:), the character between them are taken to form the name of a named character class. Such an expression expands to the literal character class denoted by the named class.

  

The following named character classes are recognized.

alpha

alphabetic characters

alnum

alphabetic characters and digits

ascii

ASCII (7-bit) characters

binary

"0" and "1"

cntrl

control characters

digit

decimal digits

hdigit

hexadecimal digits (both cases)

ident

identifier characters

ident1

leading identifier characters

lower

lowercase letters

odigit

octal digits (0-7)

space

whitespace characters

upper

uppercase letters

vowel

vowels (both cases)

Examples

withStringTools:

ExpandCharacterClassabc

abc

(1)

ExpandCharacterClassbca

abc

(2)

ExpandCharacterClass

(3)

ExpandCharacterClassa-z

abcdefghijklmnopqrstuvwxyz

(4)

ExpandCharacterClassa-z123

123abcdefghijklmnopqrstuvwxyz

(5)

ExpandCharacterClass[a-z123]

123abcdefghijklmnopqrstuvwxyz

(6)

ExpandCharacterClassa-ce-h

abcefgh

(7)

ExpandCharacterClassa-cwxyzd-h

abcdefghwxyz

(8)

ExpandCharacterClass:vowel:

AEIOUaeiou

(9)

ExpandCharacterClass:binary:

01

(10)

ExpandCharacterClass:digit:

0123456789

(11)

ExpandCharacterClass:digit:

0123456789

(12)

VisibleExpandCharacterClass^a-zA-Z

\1\2\3\4\5\6\7\8\9\10\11\12\13\14\15\16\17\18\19\20\21\22\23\24\25\26\27\28\29\30\31 !"#$%&'()*+,-./0123456789:;<=>?@[\]^_`{|}~\127\128\129\130\131\132\133\134\135\136\137\138\139\140\141\142\143\144\145\146\147\148\149\150\151\152\153\154\155\156\157\158\159\160\161\162\163\164\165\166\167\168\169\170\171\172\173\174\175\176\177\178\179\180\181\182\183\184\185\186\187\188\189\190\191\192\193\194\195\196\197\198\199\200\201\202\203\204\205\206\207\208\209\210\211\212\213\214\215\216\217\218\219\220\221\222\223\224\225\226\227\228\229\230\231\232\233\234\235\236\237\238\239\240\241\242\243\244\245\246\247\248\249\250\251\252\253\254\255

(13)

ExpandCharacterClasscat^&comma;&Iota;1&comma;32&comma;&Iota;120&comma;255

!"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvw

(14)

See Also

string

StringTools

StringTools/Regular_Expressions

 


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